Plenty of ways that you can put the new tool to good use. One would be to get to within the exact distance of the target where your rifle is zeroed.
Another would be to determine the point blank range of your rifle load and zero for a given size target. That is the distance where from the muzzle to that range, the bullet is never more than X inches above or below the line of sight from the scope. To determine that range you need the height of the center of your scope above the bore of the rifle, the muzzle velocity of your load from your rifle (this needs to be measured with a chronograph), the ballistic coefficient of the bullet that you're shooting and a ballistic program. The "X" above is the radius of the vital zone of the animal that you're trying to hit. Armed with the point blank range of your rifle, you can use the rangefinder to limit your shots to no farther than that range. At any range inside that, you simply aim at the center of the vital exactly and know that the bullet will hit somewhere in the vitals. The smaller the target, the closer the max point blank range will be.
Yet another is the idea of a "dangerzone". This is similar in concept to the point blank range but it bounded on the near side by the range where the bullet is X inches above the point of aim and the far end by where the bullet is X inches below. This will work out to a farther range than point blank and the depth of the dangerzone is determined by the zero range, target size and the ballistics of the rifle/cartridge combo. The farther the zero range, the shorter the dangerzone because the bullet is dropping rapidly at extended range. The worse the ballistic efficiency of the rifle/cartridge, the shorter the dangerzone, again, because the bullet is dropping rapidly. The smaller the target, the shorter the dangerzone because bullet has a shorter vertical distance to drop from the top of the target region to the bottom. If let's say your rifle is zeroed at 300yds and the vitals of a fox are 6" high, you might work out that the bullet is 3" above the line-of sight at 250yds and 3" below LOS at 315yds. As long as you determine that your fox is within the range of 250-315 yds, you can hold dead on and still hit the vitals.
Personal technique: Without some kind of ballistic reticule I don't want to use a holdover that takes me off the animal with a finite aimpoint. This leads to another technique for extending the effectiveness of a point-blank zero. If you know the distance from the top of the animal to the bottom of the vitals, you can extend your effective range without having to "imagine a ruler above the animal" by figuring out where, beyond your point-blank range, the bullet is the distance from the top of the animal to the bottom of the vitals below the line of sight. If the target is outside your max point-blank range but inside the range figured above, you simply place the horizontal line of the crosshair even with the top of the target and let the bullet "drop into" the vitals.
A final option is to buy and install a target turret for elevation on your scope. Kenton Industries makes them for several different brands and models of scope that take your muzzle velocity, ballistic coefficient and normal shooting elevation and temperature and produce an elevation turret marked in yds. As long as you're at or very near the atmospheric conditions for which the turret is calibrated, you simply lase the target and dial in the yardage. Where you run into problems is when you're not close to the calibrated atmospherics. At that point you need a way to measure temp and pressure and a ballistic computer or smartphone app.
